The present invention relates to a battery discharge indicator. More particularly, the present invention relates to a battery discharge indicator which indicates the voltage for the battery and automatically disconnects a load connected to the battery when the battery voltage drops below a predetermined value. Furthermore, the present invention relates to battery discharge indicators having a self-test capability.
Various devices for sensing the state of charge of a battery and for disconnecting a load connected to the battery are known in the prior art. A battery connected to a load will drive the load until the battery is incapable of supplying the current necessary for proper operation of the load. For example, a truck battery connected to a lift pump will drive the pump until the continued load of the battery causes the battery charge to be depleted so that the battery can no longer supply the required voltage for operating the pump.
Although devices are known for sensing the state of charge of a battery and for disconnecting a load connected to the battery when the charge drops below a predetermined level, these devices only warn the operator of the vehicle that the battery has discharged to a critical level and do not indicate the relative charge in the battery before the critical level is reached. Examples of such prior art devices can be found in U.S. Pat. Nos. 3,475,061; 3,568,175; and 3,786,342. Other prior art devices provide no visual indication of the state of charge of the battery so that the load continues to drain the battery of its charge until the load is automatically disconnected after the specified interval of time has expired. In either class of devices, an operator is not given the opportunity to disconnect the load from the battery and to recharge the battery before it becomes substantially depleted of its charge.
The present invention overcomes this deficiency by providing a continuous indication of the instantaneous battery voltage. By so providing a means for reading continuously and directly the exact amount of energy left in the battery, the operator of the vehicle is given the option of recharging the battery before it reaches the critical level. Additionally, if there is any malfunction in the warning and disabling circuitry which would otherwise warn of a drop in battery voltage below a critical level and disable the load a short time thereafter, there is a continuous visual indication of the state of charge of the battery.
Furthermore, conventional devices for indicating the state of charge of a battery do not have a self-testing capability. That is, these devices operate only in response to the actual rate of decay of the battery charged. Consequently, a conventional device may be defective, as manufactured, or may malfunction during the course of operation, and be unable to disconnect the load from the battery when the critical level of discharge is reached. As a result, the battery may become damaged permamently due to the continued operation below the discharge level.
For these reasons, a battery discharge indicator device is needed for indicating the state of charge of the battery and for providing the operator with an opportunity to disconnect the battery from the load so that is can be removed and recharged. Such a device should also have a self-testing capability to forewarn the indicator that it will not operate to indicate the state of charge of the battery or disconnect the load when the battery charge is sufficiently depleted.
A principal advantage of the present invention is that it provides a continuous indication of the instantaneous battery voltage thereby permitting the operator to remove and recharge the battery before it reaches a critical level and before the load is automatically disconnected.
A further advantage of the present invention is that it can automatically test itself before the battery charge has been appreciably depleted due to the operation of the load.
Other advantages appear below in the detailed description of the preferred embodiment.
For the purpose of illustrating the invention, there is shown in the drawings a form which is presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.